Electric resistance furnace



A a 9 1 6 v 0 N ELECTRIC RESISTANCE FURNACE Original Filed Jan. 23 1924Patented Nov. 6 192 8. A A

UNITED STATES- PATENT OFFICE.

ALBERT J. HANSON, OF ARLINGTON, MASSACHUSETTS, ASSIGNOR TO AMERICANMETALLURGICAL CORPORATION, OF BOSTON, MASSACHUSETTS, A CORPORATION OFMASSACHUSETTS.

ELECTRIC RESISTANCE FURNACE.

Application filed January 23, 1924, Serial No. 687,913. Renewed May 7,1927.-

This invention relates to an electric resisb bends by gravity on theirsupports, there is ance furnace. no opportunity for the weight of aresistor' One object of the invention is to provide an when at highten'iperature to cause its attenuelectric resistance furnace of noveland imation with consequent decrease of effective 5 proved construction,particularly with recross section with its result-ant danger of spect tothe supporting of the resistor Within overheating and burning out, acondition the furnace, to produce a furnace which is which it is foundin practice is liable to occur 55 simple, durable and capable of maximumWhen the resistor is suspended at its upper efliciency in operation, andalso one in which bends; the weight of the resistor then sub- 0 theliability of short-circuiting the resistor jecting it to tensionstresses which in its softand burningout the same are reduced to a enedcondition" at high temperature it is not minimum. able to withstand. Theprojecting portion on Another object of the invention is to proof oneresistor support is preferably arvi'de afurnace of the characterspecified ranged to cooperate with the upper bends of whichniay beconstructed in a simple and ina resistor section arranged beneath thesame expensive manner, and particularly one in and retain the. upper endof such lower resiswhich the resistor sections may be installed torsection in operative position, with the up 35 and removedata minimumexpense and in a per bends maintained in spaced relation.

simple and convenient manner. Provision is also preferably made forremov- A still further object of the invention is-to ably retaining thelower bends of each resisprovide a novel and improved construction torsection in their proper positions upon the of resistor support forelectric resistance furresistor support, as will be described. The 7naces. resistor support may, and preferably will, To these ends, theresistor of the electric comprise a unitary structure adapted to beresistance furnace comprises preferably the laid up between the brick ofthefurnace wall usual ribbon bent into a general sinuous in a mannersuch that a plurality of the reshape, having a plurality of bends atopposite sistor supports cooperate to form a projectsides thereof, andthe resistor support coming shelf for supporting the resistor sections.prises a body of electrical insulating mate- These and other featureswill be herein- 30 rial, preferably having high thermal transafterdescribed, and particularly pointed out mitting and radiatingproperties, and which in the claims at the end of the specification. ispreferably embedded in and arranged to In the drawings illustrating thepreferred 30 project from a wall of theheating chamber of embodiment ofthe invention, the furnace to support the resistor thereon. Figure 1 isa perspective of. the improved In the preferred embodiment of the inven-.resistor support. tion, the resistor support comprises a pre- Figure 2is a section on line 22 of F ig formed tile adapted to be laid upbetween the ure 1. brick in'a wall of the heating chamber of the Figure3 is a perspective of one of the defurnace and to project from the wallto form, vices for retaining the resistor upon the re- 40 in effect, asupporting shelf. Each resistor sistor support.

section is preferably arranged to be sup- Figured is a vertical sectionof a portion ported upon and to rest directly upon the proof the wall ofthe heating chamber, illustrat-- jccting portion of the resistorsupport-wand ing the resistors and their manner of supthe latterpreferably has provision for mainport.

45 taining the bends of the resistor in spaced re- Figure 5 is a frontView of a portion of the lation to one another and in spaced relationface of the Wall illustrated in Figure 4c; and to the wall of theheating chamber. By sup- Figure 6 is a perspective of one of theauxilporting the resistors by resting their lower iary supports to bereferred to.

Referring to the drawing, represents a portion of one wall of theheating chamber of an electric resistance furnace, which may be of theusual construction, and 12 a resistor of any usual or preferredconstruction. Preferably as illustrated in Figure 5, it comprises theusual nickel chromium ribbon of a general sinuous shape having aplurality of bends 13, 14 at the opposite sides thereof. The resistor 12is preferably built in sections, which are installed in the furnace andelectrically connected in any well known manner. In accordance with thepresent invention, the sections of the resistor 12 are supported uponthe wall 10 of the heating chamber of the furnace by preformedinsulating supporting members 15 embedded in the wall and havingportions 16 projecting from the face of the wall and upon which theresistor sections are supported. As herein shown, the

. resistor supports which comprise preformed tiles of electricalinsulating material, such as carborundum, crystolon, or similar materialhaving high electrical insulating properties at high temperatures, and,in addition,

good thermal transmitting and radiating.

properties, are laid up between adjacent brick in the construction ofthe wall of the heating chamber, as illustrated in Figure 4.

Provision is made for removably mounting the resistor sections inoperative substantially upright position upon the projecting portions 16in a novel manner to permit the sections to be installed and removed ina simple and convenient manner, and for this purpose as herein shown,the resistor supports 15 are arranged to project from the face of thewall to form a series of transversely extending shelves arranged oneabove the other and spaced from one another slightly more than theheight ofthe resistor section 12 which it is desired to employ. Aresistor section is arranged to rest upon the upper surfaces of theresistor supports 15 forming each shelf,

and the under portions of the resistor supports of the next higher shelfare constructed to cooperate withthe upper ends of the resistor sectionto retain it in operative position while supported on the next lowershelf.

Provision is also made for spacing the individual bends 13, 14 or partsof each resistorsection from one another, and also'from the wall of the.furnace, and as illustrated in the drawing, both the upper and lowersurfaces of the projecting portions 16 of the resistor supports 15 areprovided with grooves 25, 26 of a size. sufficient to receive the upperand lower bends 13, 14 of the resistor. The grooves 25 and 26 are spacedapart in staggered or ofiset relation to pro vide intervening bodies 28,29 of insulating material, and the walls of the grooves also serve torestrain the sections from transverse movement. The forward ends of thegrooves 25 in the under surface of the resistor supports 'are closed byretaining members 30 preferably comprising a part of the front wall 31of each support, as illustrated in Figure 1, and which cooperate withthe upper bends 13 ofthe resistor to prevent forward displacementthereof. By reference to Figures 4 and 5, it will be seen that eachresistor section is supported upon a resistor support with the lowerbends 14 thereof resting in the grooves 26 in the upper surface of theresistor support, and that each section is retained at its upper endwith the upper bends 13 loosely received in the grooves 25 in the undersurface of the next higher resistor support, by the members 30 closingthe forward ends of the grooves. In order to prevent displacement of thelower bends 14 of each resistor section, a series of lips 34are'preferably provided at the forward ends of the insulating portions29 between the grooves 26 in the upper surface of the resistor support,as illustrated in Figures 1 and 2, and one or more transverselyextending retaining members 36, preferably of lava, or other refractorymaterial havin electrical insulating properties and pref transmittingand radiating properties, rests upon the upper surface of the resistorsupport immediately in front of the resistor section and between it andthe lips 34. The retaining members 36 are held in place by gravity, andare prevented from forward displacement by the lips 34. i

In order to insulate the resistor sections from the face of the wall ofthe heating chamber, the-resistor supports 15 are preferably laid up inthe wall in a manner such as to cause the rear ends 38 of the grooves25, 26, and consequently the rear of each resistor section, to be spaceda short distance from the face of the wall, as'illustrated in Figure 4.

In practice, the resistor supports 15 are, as has been stated, composedof carborundum or other similar material, having high electricalinsulating properties at high temperatures, and good thermaltransmitting and radiating properties, and the resistor supports arepreferably cast in the form illustrated in Figure 1, having the grooves25, 26 in the upper and lower surfaces thereof offset to permit theresistor supports to be laid up one above the other and to have thegrooves 25,26 in the correct position to receive the upper and lowerbends 13, 14 of the usual sinuous shaped resistor, such as isillustrated in Figure 5. This construction of resistor supporting member15 possesses strength, and there is therefore little liability ofitsfracture during the normal use of the furnace.

In the construction of the electric resistance furnace, the precastresistor-supporting members 15 are shipped to the job and laid upbetween the fire brick comprising the face of the wall of the heatingchamber to form an erably good thermal the two inch integral part of thewall. In practice, the resistor supports are preferably castsubstantially one inch in thickness, so that using the usual two inchbrick, the mason by laying up the resistor supports with a double courseof rick intervening, provides a distance between the resistor supportsof substantially five inches, this being slightly greater than theheight of the resistor sec tion commonly employed. In order to installthe resistor sections, the workman bends the resistor ribbon into thedesired shape,

preferably the sinuous shape illustrated in Figure 5, and thereafterinserts the upper bends 13 of each section in the grooves 26 on theunder side of the upper resistor support. It is possible to do this byinclining the resistor section and slipping the upper bends beneath themembers 30, closing the forward ends of the grooves 25. When the upperbends 13 of the resistor section have been thus placed in the ooves 25,the lower bends '14 are slid into t e grooves 26 upon the upper surfaceof the lower resistor support, the grooves 26 being open at theirforward ends readily permittlng this to be done. Thereafter the operatorsimply drops the retaining members 36 in position, in front of theresistor section, the members being retained by gravity in theiroperative position and prevented from forward displacement by theretaining lips 34: projecting from the surface of the resistor support.It will therefore be apparentthat the resistor sections may be installedin an exceeding simple and practical manner, in-a-minimum of time, andat a relativelysmallexpense. In a similar manner,

they may be easily and conveniently removed,

all that is required being for the operator to remove the retainingmembers 36, to slide out the lower ends of the resistor sections, andthen drop the sections down until the upper' I bends 13 clear themembers 30 which close the front of the grooves 26.

In order to insure against the possibility of saggingof the upstandingloops of the re sistor sections when the furnace is operatedthe grooves25 upon the uppersurface of the resistor support. 'The auxiliarsupporting members 40*comprise preforme members of insulating material,preferably carborundum orsimilar material having high electrical insulating properties and good thermal transmitting and radiatingproperties, and are preferably of a tapered shape, as illustrated inFigure 6. The members 40 are removably' retained in anoperative positionby the upstanding lip 34 and by the members 30 closing the forward endsof the grooves 26 on the lower surfaces of each resistor support, asillustrated in Figure 4. While during the By reference toFigure 4, itwill be seen that the resistor supports project forwardly from the wallof the heating chamber beyond the resistor sections, and the projectingportions together with the upstanding lips 34 serve to protect theresistor sections against mechanical damage or breakage from impact withanything which may tip over within the furnace. observed that the upperand lower bends 13, 14 of each section of the...resistor are spaced fromeach other'by bodies 28, 29 of electrical insulating material, andfurthermore in the preferred construction of resistor support, the lowerbends 14 of one section of the resistor are separated from the, upperbends 13 of the next lower resistor section by an intervening body ofelectrical insu lating material comprising the body portion of theresistor support itself, and as a result, the liability ofshort-circuiting of the resistors is reduced to a minimum.

The present construction of electric re sistance furnace is designed toreduce to a'minimum, the liability of burning out the resistor. Themanner of supporting the resistors, it will be observed, is such as toexpose them for direct radiation into the heating chamber of thefurnace, so that when the furnace is operated at high tem perature theheat is radiated directly into the heating chamber'where it is utilizedand the accumulation of heat and the building up of excessivetemperatures in the immediate vicinity of the resistor is avoided. Thisconstruction therefore is conducive to the long life of the resistors.

It is also to be observed that in the present construction of furnace,the resistor sections 'are supported in a manner such that a maximumamount of wall space may be utilized for the resistors, producing afurnace having a maximum electrical capacity per square foot of wallspace.

The term sinuous as usedthroughout the specification and claims, is tobe understood is including shapes of resistors having closed bendsof,various shapes at the opposite sides thereof.

WVhile the referred embodiment of the invention has een illustrated anddescribed, it is to be understood that the different features of theinvention may be embodied in other forms within the scope of thefollowing claims.

I claim:

combination, a chamber Wall, a resistor section having a plurality ofbends at two of the opposite sides thereof, insulating membersprojecting from the wall on opposite 1. In an electric, resistancefurnace, in

It will also be 7 wall.

sides of the resistor section and having spaced apart recesses inadjacent surfaces, and means cooperating with said bends for retainingthem in'the recesses and the resistor section in place upon the chamberand the section in place upon the chamber wall.

3. In an electric resistancev furnace, 1n

combination, a chamber wall, a resistor sec-.

tion having a plurality of bends upon two of the opposite sidesthereof,insulating members projecting from the wall on opposite sides of theresistor section and havingrecesses in adjacent surfaces, and meanscooperating with said bends to retain the section in operative positionbetween said insulating members and having provision for permitting oneside of the section to be moved forwardly upon the insulating member toremove the section from between said insulating members.

4. In an electric resistance furnace, in combination, a chamber wall,two insulating members spaced apart and projecting from the wall, aresistor section having bends at two of its opposite sides arrangedbetween said insulating members, and means for retaining the resistorsection between said insulating members including recesses in theadjacent surfaces of the insulating members in which the bends arereceived,

means carried by one of the insulating members for preventing forwarddisplacement of one set of bends from one set of recesses, and removablemeans for preventing displacement of the second set of bends from thesecond set of recesses.

5. In an electric resistance furnace, in combination, a chamber -wall,two insulating members spaced apart and projecting from the wall, aresistor section having a plurality of bends at two of its oppositesides, and means for retaining the resistor section in operativeposition between the insulating members including grooves in theadjacentsurfaces of the insulating members in which said bends are received, oneset of grooves being closed at their forward ends and the second setbeing open, and removable means for retaining the bends in the opengrooves. v

6. In an electric resistance furnace, in combination, a chamber wall, aresistor section of general sinuous shape having upper and lower bends,and meansfor removablv supporting the resistor section upon the wallineluding insulating members projecting from the wall above and belowsaid section, relating pockets in the under surface of the upperinsulating member in which said upper bends are received and preventedfrom displacement by the walls, recesses in the upper surface of 8. Aresistor support for electric resistance furnaces, comprising a tile ofelectrical insulating material provided upon its under surface with aplurality of grooves spaced apart and closed at one end, and having uponits upper surface a plurality of grooves open at one end. I

9. A resistor support for electric resistan' e furnaces, comprisingatile of electrical insulating material provided with grooves onopposite surfaces thereof spaced apart and with the grooves upon onesurface arranged intermediate adjacent grooves upon the othersurface,-and provided with members projecting above one surfaceof thetile, for the purpose specified.

10. In anelectric resistance furnace, in combination, a chamber wall,resistors each having a plurality of upper and lower bends, and aresistor support of insulating material embedded in the wall and havinga portion projecting therefrom-provided with depressions in its uppersurface in which the lower bends of the resistor rest and depressions inits lo\v er surface to receive the upper bends of the resistors below,said depressions being spaced apart to provide intervening bodies ofinsulating material between said bends.

11. In an electric resistance furnace, in combination, a chamber wall,resistors eachhaving a plurality of upper and lower bends, and aresistor support of insulating material embedded in the wall and havinga portion projecting therefrom provided with depres-- sions in its uppersurface in which the lower bends of the resistor restanddepressions in Iits lower surface to receive the upper bends of the resistors below,said depressions being spaced apart to provide intervening bodies ofinsulating material between said bends, and said depressions in theupperand lower surfaces being staggered relative to each other.

12. A resistor support having grooves to Inn receiveand support'thelower bends of a sinutween 'said grooves to hold in position a resistorretalmng element.

13. In combination, a furnace having a re- I sistor support projectingfrom a wall thereof, 5 said support having grooves extending inupwardlybetween said grooves along its outer edge, and a bar extending alongsaid edge back of said lips and engaging the forward edge ofsaid'resistorto retain said bends in said grooves.

In testimony whereof I have aflixed my signature.

- ALBERT J. HANSON.

